The present invention generally relates to electrochemical cells and, more particularly, relates to an electrochemical cell having an increased anode-to-cathode interface area.
Electrochemical cells are commonly employed to supply voltage for electrically operated devices, and are particularly well-suited for use with portable electrically operated devices. Currently, the popular conventional alkaline cells are of a generally cylindrical type which are commercially available in industry standard sizes including D-, C-, AA-, AAA-, AAAA-size cells, as well as other sizes and configurations. Electrochemical cells, such as the aforementioned cylindrical type, commonly provide for a predetermined open circuit voltage supply.
Conventional cylindrical alkaline cells generally have a cylindrical-shaped steel can provided with a positive cover at one end and a negative cover at the opposite end. The cylindrical cell has a positive electrode, commonly referred to as the cathode, which is often formed of a mixture of manganese dioxide, potassium hydroxide solution, water, and other additives, formed about the interior side surface of the cylindrical steel can. A cup-shaped separator is centrally disposed in an inner cylindrical volume of the can about the interior surface of the cathode. A negative electrode, commonly referred to as the anode, is typically formed of zinc powder, a gelling agent, and other additives, and is disposed with the electrolyte solution within the separator. The aforementioned cylindrical cell is commonly referred to as a bobbin-type cell, one example of which is disclosed in U.S. Pat. No. 5,501,924, which is hereby incorporated by reference.
Conventional bobbin-type cells of the aforementioned cylindrical type have a single cylindrical anode and single cathode contained within the steel can and separated via the cup-shaped separator. The cathode is usually disposed adjacent to the interior side wall of a steel can, while the anode is disposed within a cylindrical cavity provided in the cathode. Accordingly, the conventional cell has a cylindrical anode-to-cathode interface surface area generally defined by the shape and size of the anode and the cathode. With the conventional cylindrical cell, the anode-to-cathode interface area is approximately equal to the surface area of the cylindrical cavity formed in the cathode, into which the separator is disposed. In addition, the anode is generally provided in the shape of a cylinder with a uniformly curved outer surface generally formed parallel to the container wall such that the cathode is not easily susceptible to breakage which can lead to ionic and electric discontinuity within the cell.
A primary goal in designing alkaline cells is to increase the service performance which is the length of time for the cell to discharge under a given load to a specific voltage at which the cell is no longer useful for its intended purpose. A further goal in designing alkaline cells is to increase the high rate performance of the cell. Commercially available alkaline cells commonly have an external size that is defined by industry standards, thereby limiting the ability to increase the amount of active materials that can be utilized. Yet, the need to find new ways to increase service performance remains a primary goal of the cell designers.